Wires coated with hard particles, such as diamond dust, and utilized as a saw are conventional. Such saws, so-called wires saws, are forms which are open at both ends because it has not been possible heretofore to produce endless wires without a weld seam. Such saw wires would be breakable at the weld seams. By increasing the wire length coated with relatively hard particles, the number of switchovers per unit time can be reduced for a reciprocating sawing motion. This results in an increased lifetime for these saw wires.
This realization has been exploited for years. The saw wire is called a diamond saw wire. However, it has not completely proven itself in its previous design. It wears very quickly. During the sawing operations, the diamond particles are torn out and the base material has become so brittle by the coating process that the saw wire, due to rupture, not only fails but is entirely useless.
It has been found by detailed testing that even the application of diamond dust by rolling, with the aid of a pair of rolls of hardened steel, does not provide the desired success. Although, such a wire saw exhibits a longer life, the diamond dust, though, cannot be rolled on the wire, serving as the basic member, with a required uniformity, so that the cutting properties of the wire do not afford the expected improvements.
A process has been known from German Pat. No. 2,303,897 for the manufacture of a cutting tool for stone wherein a strip is first provided with oil or grease along the narrow sides and then passes through a station with diamond grains wherein the grains adhere to the zones coated with oil or grease. In the subsequent rolls, the grains are then pressed into the strip. Then, the strip is mechanically twisted, and the thus-twisted strip is hardened in a heating device. By the use of a soft strip, pressing-in of the diamond grains is simplified. But, thereafter hardening of the strip is necessary. This latter step is very difficult, because in case of too high a hardening temperature, the diamond bodies can sustain irreparable damage. Furthermore, the application of the diamond grains to zones provided with oil or grease can be disadvantageous, because the zones cannot be exactly defined, and can readily be blurred by external influences during the manufacturing process. Finally, it is necessary in the known process to produce the free spaces required for removing sawdust by the twisting of a strip, so that, in total, a precise saw cut free of chatter marks cannot be obtained.
In constrast, the invention is based on the object of providing a process permitting the attachment of even harder particles, such as diamond dust or the like, without disadvantage to wire-like, hardened base material, in such a way that a diamond dust is not harmed. This process establishes a reproducible coating of any kind, especially a coating coherent over the length of the wire. This coating is of a microscopically homogeneous character and can be fashioned so that vacant spaces for removal of sawdust are produced while simultaneously preserving the wire structure as a cylindrical body so that highly precise cuts can be performed with smooth cutting surfaces.
This object has been attained by the features set forth in the claims.
Along these lines the process of this invention is distinguished in that form is brought into contact, under pressure, with a surface of two rolls, at least partially provided with the particles to be applied, while the wire-like form is being rotated about its longitudinal axis.
This process makes it possible to manufacture plain or multiple wire saws according to this invention.